When someone is so much a part of your life they leave little seeds in you, and a little part of you changes to become like the one. It could be the way you now say certain words a different way. Maybe now you type "mm kay" or say "yeah, go for it". Maybe it's a taste for rock music you've acquired, or strawberry-flavoured stuff, or hazelnut coffee. Maybe you swear more now. Maybe you grew to like driving out to the seaside. Perhaps you've developed a sense of humour. Maybe it's not even in the recognisable habits; the person has changed who you are. Maybe you've come to be a more introspective person. Or more dependent on others.
It doesn't have to be someone you've spent a lot of time with. It could just be someone you really like, or look up to. When you look up to someone you might imitate certain aspects of them without realising. You give these people a certain amount of influence over yourself.
The weight of your entirety might have left me but you still remain in the little, the everyday. I only eat seedless grapes. I never drink Yeo's green tea anymore, only Heaven and Earth. And yeah, I still like beer. Perhaps a little too much now. I also still go to see the cats. I still walk the route we used to take, and the cats are still there. And you are in the wind of every storm.